It's because it thinks you're activating them on a new computer, and you can only activate Arturia products on five computers at once, which is quite generous I guess. Until recently, you could only release used activations by raising a service ticket, but after myself and no doubt a load of other people hounded Arturia about it, you can now do this from your profile. Log into the main site, look under My Products, then click 'More Info' in green on the right hand side next to the product(s) you want to manage. From there you'll see the computers the product(s) activated on, along with buttons to deactivate the licences on a device-by-device basis. In your case it's probably best to deactivate the all the licences on all your products and start again, by reactivating them through the Arturia Software Center.
Arturia never really considered there are PC users out there who change their core hardware as often as they change their underwear. But at least this is a solution for you nerdy PC-building types
